DE102022132960B4 - Process for producing molten iron and liquid slag in an electric melter - Google Patents

Abstract

Method for producing an iron melt (1) and a liquid slag (2) in an electric melter (10) with at least two electrodes (11), comprising the steps of:- feeding the melter (10) with iron-containing materials, carbon-containing materials and slag formers via several feeding points (12);- melting the iron-containing materials, carbon-containing materials and slag formers to produce an iron melt (1) and a liquid slag (2) arranged on the iron melt (1);- tapping the liquid slag (2) and the iron melt (1); characterized in that the charging of the carbon-containing materials takes place in several sequences and per sequence only via a part of the charging points (12), wherein during charging, material cones (17) are formed below the charging points (12), so that during melting of the carbon-containing materials charged per sequence, not all electrodes (11) are brought into contact with the material cone or cones (17), wherein at least one electrode (11) is in contact with the material cone (17) which contains or consists of carbon-containing materials.

Description

The invention relates to a method for producing molten iron and liquid slag in an electric smelter.

Methods and devices for producing iron melts and liquid slags in electric melters are state of the art, see among others US 3 385 494 A . Similar methods and devices are described in the publications DE 15 83 194 A , DE 218 957 A and DE 26 10 592 A1 revealed.

A method for producing an iron melt which is carburized during the melting process in an electric melter by means of carbon-containing substances is described by way of example in the EN 10 2022 118 640 A1 The aim is to specifically inject carbon into the cohesive zone, in which the carbon can optimally dissolve in the molten iron, thus resulting in carburization of the molten iron or an increase in the carbon content in the molten iron.

The object of the present invention is to further develop this method in such a way that it can be easily implemented and, in particular, can ensure optimum melting performance of the electric melter.

This object is achieved by a method having the features of claim 1. Further embodiments are described in the subclaims.

The invention relates to a method for producing an iron melt and a liquid slag in an electric melter with at least two electrodes, comprising the steps of: - feeding the melter with iron-containing materials, carbon-containing materials and slag formers via several feeding points; - melting the iron-containing materials, carbon-containing materials and slag formers to produce an iron melt and a liquid slag arranged on the iron melt; - tapping the liquid slag and the iron melt; wherein the carbon-containing materials are fed in several sequences and per sequence only via a portion of the feeding points, wherein during the feeding, cones of material form below the feeding points, so that during the melting of the carbon-containing materials fed per sequence, not all electrodes are brought into contact with the cone(s) of material.

To melt the solid materials, the electric melter has at least two electrodes, which are supplied with electrical current and thus provide the energy required to convert the solid materials into molten iron and liquid slag. Depending on the size/dimensions of the electric melter, several electrodes can also be used, for example three, four, five, six or more than six.

If the electrodes are positioned in the molten iron or liquid slag during melting or melting operation, or at a distance above it in order to ignite an arc, the resistance and thus also the heat input can be increased. A high heat input is preferable in order to achieve optimum melting performance of the electric melter. The inventors have determined that this procedure is not sufficient to achieve optimum carburization of the molten iron when fed with carbon-containing materials in the conventional way.

The invention makes use of the fact that at least one electrode is in contact with the cone of material which contains or consists of carbonaceous materials, or is surrounded by it or is immersed in it. This allows optimal carburization to take place, since the carbon in the carbonaceous materials of the cone of material or in the cone of material can dissolve directly in the molten iron through contact with the electrode at high temperatures. At least one of the other electrodes is immersed in the molten iron or liquid slag or forms an arc above the liquid slag, whereby not all electrodes (may) touch the (same) cone of material.

The electrode or electrodes which are in contact with the cone(s) of material is or are positioned above the molten iron or liquid slag according to one embodiment. This ensures that the energy which is provided by the (respective) electrode(s) by applying current is used to melt the carbon-containing materials in or into the cone(s).

The electrode or electrodes which are not in contact with the cone(s) of material are positioned in the molten iron or liquid slag or less than 150 cm, in particular less than 120 cm, preferably less than 100 cm above the molten iron or liquid slag. This achieves the necessary resistance to ensure optimum melting operation with optimum melting performance. If the current application or the current flow is too high and thus the resistance heating is too low, at least one of the electrodes can be raised, which is, for example, immersed or positioned in the molten iron or liquid slag, so that an arc is formed. The greater the distance between the electrode and the molten iron or liquid slag, which can be up to 150 cm, in particular up to 120 cm, preferably up to 100 cm, the higher the electrical resistance. The expert knows how to optimally determine or select the distance in order to be able to form a stable arc. The distance can, for example, be greater in direct current operation than in alternating current operation.

According to a further embodiment, the loading per sequence is carried out in such a way that at least one layer of carbon-containing materials and at least one layer of iron-containing materials are applied to the liquid slag or molten iron as a cone of material. This allows optimal carburization to take place, since the carbon in the carbon-containing materials can dissolve directly in the molten iron due to the direct contact with the electrode and the resulting high temperatures.

According to a further embodiment, the loading per sequence and the positioning of the pouring cones and/or the positioning of the electrodes are visually monitored by means of at least one camera. This ensures that the electrode or electrodes which are in contact with the carbon-containing materials are correctly positioned.

According to an additional or alternative embodiment, the loading per sequence and the positioning of the cones and/or the positioning of the electrodes can be monitored by means of at least one pyrometer. The pyrometer(s) detect the electromagnetic radiation emitted by the cone and/or the liquid slag or the molten iron, which is proportional to the temperature of the cone and/or the liquid slag or the molten iron, which can contribute to the control of the loading and/or positioning.

According to a further embodiment, the electrodes can be individually supplied with current. This means that the level of the current flow can be adjusted as required depending on the positioning of the electrodes, whether they are in contact with the pile of material or are immersed in the molten iron or liquid slag or are positioned above it.

According to a further embodiment, the charging of the carbon-containing materials changes per sequence in such a way that, depending on the sequence, each electrode is temporarily in contact with a cone of material or is immersed in the molten iron or liquid slag or is positioned above it (above) at a distance of up to 150 cm, in particular up to 120 cm, preferably up to 100 cm. As a result, the area for carburization changes locally while at the same time maintaining a sufficiently high electrical resistance. This preferably generates homogeneous carburization within the molten iron. The alternating charging preferably takes place shortly before tapping, whereby it enables the carbon content of the molten iron to be increased to a desired target range. The flexible electrode guide can also achieve an optimized bath movement, which in turn can bring about improved mixing of the molten iron.

The electric melter is preferably an OSBF (Open Slag Bath Furnace) furnace. These include electric arc furnaces, especially SAF (Submerged Electric Arc Furnace), which are melting furnaces with arc resistance heating that form arcs between the electrode and the solid and/or slag or which heat the solid and/or slag using the Joule effect. In the SAF, the electrode (or electrodes, if there are several) is immersed in the solid and/or liquid slag. Depending on the functional principle/mode of operation, the electric arc furnaces can be designed as alternating current arc reduction furnaces (SAFac) or direct current arc reduction furnaces (SAFdc). Alternatively, melting furnaces with direct arc exposure, which deviate from the functional principle/mode of operation described above, so-called EAF (Electric Arc Furnace) can be used, which form arcs between the electrode and the metal. This includes the alternating current arc melting furnace (EAFac), the direct current arc melting furnace (EAFdc) and the ladle furnace LF (Ladle Furnace).

The process is particularly preferably carried out in a reducing atmosphere.

The invention is explained in more detail using the following embodiments in conjunction with the drawing.

In 1 The invention is explained using the example of an electric melter (10) with at least two electrodes (11) in a schematic side view. The electric melter (10) comprises a vessel (15) into which iron-containing materials, carbon-containing materials and slag formers are fed via several charging points (12). is fed. The iron-containing materials, carbon-containing materials and slag formers are melted to produce an iron melt (1) and a liquid slag (2) arranged on the iron melt (1). The carbon-containing materials are fed in several sequences and only via a part of the feed points (12) per sequence. This type of feeding of the carbon-containing materials ensures that not all electrodes (11) are brought into contact with the carbon-containing materials during the melting of the carbon-containing materials fed per sequence. In the 1 It is easy to see that in this example only one of the electrodes (11), the right electrode (11), which is in contact with the carbonaceous materials fed per sequence, is positioned within the cone of material (17) or above the liquid slag (2) in such a way that the cone of material (17) accumulates around the electrode (11) during feeding. The other two electrodes (11) are less than 150 cm above the liquid slag (2), middle electrode (11) in 1 , and in the liquid slag (2), left electrode (11) in 1 , positioned. It is also conceivable to position the two electrodes (11), which are not in contact with the carbonaceous materials fed per sequence, either in the liquid slag (2) or less than 150 cm above the liquid slag (2).

At least two, in this embodiment there are three electrodes (11) supply the energy required for melting. The positioning of the electrode (11) can be adjusted vertically, see double arrows. In order to achieve reliable carburization of the iron melt (1) by feeding the carbon-containing materials, it is essential that during the melting of the carbon-containing materials fed per sequence, not all electrodes (11) are brought into contact with the carbon-containing materials in the cone of material (17). What is not shown is that the feeding per sequence and the positioning of the cones of material (17) and/or the electrodes (11) are monitored by means of at least one pyrometer (not shown) and/or visually by means of at least one camera (not shown). The loading per sequence can be carried out in particular in such a way that at least one layer (17.1) of carbon-containing materials and at least one layer (17.2) of iron-containing materials are applied to the liquid slag (2) or iron melt (1) as a cone of material (17). Alternatively, the iron-containing and carbon-containing materials can be mixed, almost as a mixture, and applied to the liquid slag (2) or iron melt (1) as a cone of material (17).

The electric melter (10) can comprise a lid (16) which can close the vessel (15) at the top and thus a defined or targeted, preferably reducing atmosphere can be set within the electric melter (10). The lid (16) can be arranged so that it can be moved essentially vertically, see double arrow. If a lid (16) is present, the charging points (12) are openings in the lid (16) with corresponding supply lines. The required ferrous materials, carbonaceous materials and slag formers can be supplied via means not shown. After charging, so-called cones of material (17) are formed in the vessel (15) below the charging points (12). The ferrous materials preferably consist of or comprise sponge iron. In addition, other ferrous materials, such as ferrous scrap, can also be supplied, for example in order to increase the recycling rate. The slag formers, for example lime, silicon dioxide, magnesium oxide and/or aluminum oxide, are mixed in, especially if the so-called gangue of the preferably used iron sponge is not sufficient to be able to adjust the desired basicity of the liquid slag (2) to be tapped. The adjustment of the desired basicity by appropriate mixing/addition of slag formers is familiar to the expert. The amount of solids added depends on the desired output of the iron melt.

The electric melter (10) is preferably an OSBF, which requires electrical energy for melting, which can preferably be generated from renewable energy (sun, wind, water) in order to be able to reduce the CO ₂ balance of the melting process, for example. Once the solid materials fed in have been completely melted and in particular the specifications for the molten iron (1) and liquid slag (2) have been met, molten iron (1) and liquid slag (2) are arranged in the vessel and on the molten iron (1) and ready for tapping.

The liquid slag (2) is tapped off via, for example, a tapping point (13) and the molten iron (1) is tapped off via a tapping point (14) in the vessel (15).

2 shows a schematic view of the electric melter (10) or cover (16) using the example of the design in 1 The three electrodes (11) are arranged relatively centrally and the feeding points (12) are distributed locally at a radial distance from the electrodes (11). For example, six feeding points (12) are arranged in 60° sections in a circle around the electrodes (11).

Not shown, nozzles can be arranged in the vessel (15), in particular in the bottom of the vessel (15), to influence the movement of the molten iron (1). The electric melter (10) can also be pivotally mounted to allow tipping and thus tapping of liquid slag (2) in one direction and molten iron (1) in the other direction. The operation of electric melters (10) is also familiar to those skilled in the art.

Also not shown is how the iron melt (1) is removed and fed to a further processing step. The iron melt (1) is preferably fed to a treatment in order to reduce the carbon in the iron melt (1) to a desired level. This is done, for example, using oxygen in a so-called oxygen blowing process, particularly preferably in a converter. The tapped liquid melt (2) is also preferably fed to a granulation process in order to produce slag, in particular for the construction industry.

Claims (8)

Method for producing an iron melt (1) and a liquid slag (2) in an electric melter (10) with at least two electrodes (11), comprising the steps of: - feeding the melter (10) with iron-containing materials, carbon-containing materials and slag formers via several feeding points (12); - melting the iron-containing materials, carbon-containing materials and slag formers to produce an iron melt (1) and a liquid slag (2) arranged on the iron melt (1); - tapping the liquid slag (2) and the iron melt (1); characterized in that the charging of the carbon-containing materials takes place in several sequences and per sequence only via a part of the charging points (12), wherein during charging, pouring cones (17) are formed below the charging points (12), so that during melting of the carbon-containing materials charged per sequence, not all electrodes (11) are brought into contact with the pouring cone or cones (17), wherein at least one electrode (11) is in contact with the pouring cone (17) which contains or consists of carbon-containing materials. Procedure according to Claim 1 , wherein the electrode (11) or electrodes (11) which is or are in contact with the cone(s) of material (17) is or are positioned above the molten iron (1) or liquid slag (2). Method according to one of the preceding claims, wherein the electrode (11) or electrodes (11) which are not in contact with the cone(s) (17) are positioned in the molten iron (1) or liquid slag (2) or are positioned less than 150 cm above the molten iron (1) or liquid slag (2). Method according to one of the preceding claims, wherein the charging per sequence is carried out in such a way that at least one layer (17.1) of carbon-containing materials and at least one layer (17.2) of iron-containing materials are applied to the liquid slag (2) or molten iron (1) as a cone of material (17). Method according to one of the preceding claims, wherein the loading per sequence and the positioning of the pouring cones (17) and/or the electrodes (11) are monitored visually by means of at least one camera. Method according to one of the preceding claims, wherein the loading per sequence and the positioning of the pouring cones (17) and/or the electrodes (11) are monitored by means of at least one pyrometer. Method according to one of the preceding claims, wherein the electrodes (11) can be individually supplied with current. Method according to one of the preceding claims, wherein the charging of the carbonaceous materials per sequence changes such that, depending on the sequence, each electrode (11) is temporarily in contact with a cone of material (17) or is immersed in the molten iron (1) or liquid slag (2) or is positioned above it at a distance of up to 150 cm.

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